Fiberglass Boat Inspection


Is Your Hull Waterlogged By Osmosis?

What Is Osmosis? Water seeps into your boat's hull (often through tiny stress fractures associated with the various fittings and fastenings attached to the hull and deck) and travels via capillary-like action along layers of the fiberglass and resin laminated structure (or fiberglass and balsa wood sandwich) to accumulate in trapped pockets.

Prolonged osmosis, if undetected and untreated, can seriously shorten the lifetime of your valuable boat, and reduce its resale value. For racing craft especially, the additional hull weight due to absorbed water could be disastrous.

Gel Coat Blistering

Chemical reactions take place between water absorbed by osmosis, and water soluble molecules in fiberglass-composite hull structures. This causes surface blistering of the gel coat. The blisters are usually below the waterline and will swell and contract due to temperature changes. If unchecked the bubbles will enlarge and hull deterioration will escalate as blisters open and admit even more water.


Osmosis + Blistering = Hull Delamination


Protect Your Investment With An Electrophysics Meter

Early warning of osmosis before visible blistering. Monitor hull dryness (de-humidification repairs, painting). Identify and trace deck and bulkhead leaks. No pins, no holes, no drilling. Use one meter for both fiberglass and wood. Electromagnetic sensing unaffected by temperature. Objective, reliable, and affordable.


Model CT33 Analog Meter

The CT33 has been a popular model for fiberglass since the 1990s.
To learn more about this meter in marine use visit the web site of the renowned sailor "R.C."

Our other models designed for fiberglass are shown below.





The GRP33plus uses the same high-precision electronics as the GRP33
previously made exclusively for, and sold only by, J.R. Overseas.
Fine-tuned for best results with fiberglass

This pinless moisture meter from Electrophysics has something for everyone. The versatile GRP33plus combines the best features of the GRP33 and the popular FiberNaut, and also senses to one inch depth. The GRP33plus has three large easy to read scales. The fiberglass (FRP) scale covers the vital range of moisture contents from 0 to 3%, while the wood scale is calibrated from 0 to 30%--the range most critical for proper wood drying. A third color-coded scale gives at-a-glance indication of "good" or "bad" moisture content. The comprehensive manual with detailed guide to boat inspection for owners and professionals includes extensive wood species compensation and moisture content information for woodworkers. Ideal for boat owners, marine surveyors, and anyone who works with wood. With clip-on wrist strap and 9-volt battery.


Every GRP33plus has a unique serial number and Calibration Certificate

Available from Electrophysics or eBay.




Model GRP200 Digital Meter
Direct Reading Of Fiberglass (GRP) % Moisture Content

More Information: GRP200 & Optional Remote Sensor

The Dolphin
With Audio Moisture Level Indication
And Fiberglass % Conversion Chart

Available from Rayplex